Bottle cap made from a material comprising polypropylene, particulate calcium carbonate and additives

ABSTRACT

An injection moulded polymeric household bottle cap made of a polypropylene composition comprising: particulate CaCO 3 ; additive; and polypropylene; wherein the polypropylene composition in its solid form and with average wall thickness T has a flexural modulus, measured according to ASTM D790-07, being at least 95% of the flexural modulus measured on a reference polypropylene composition being substantially free of CaCO 3  and having average wall thickness of at least T+10%.

FIELD OF THE INVENTION

The present invention relates to an injection moulded, polymeric bottlecap made from a material comprising polypropylene, particulate CaCO₃ andadditives; such cap material having an improved flexural modulus.

BACKGROUND OF THE INVENTION

Containers, and more specifically bottles, are widely used in theconsumer goods industry for packaging various types of fluid products,such as drinks, foodstuffs, laundry and household cleaning products,shampoo and other personal care products. Thermoplastic materials aremostly used for producing these containers. Typical thermoplasticmaterial used for producing containers and bottles includepolyvinylchloride (PVC), polyethylene terephthalate (PET), polypropylene(PP), low or high density polyethylene (LDPE or HDPE) and polystyrene(PS).

Such containers, and more specifically bottles, are required to havecertain properties. Indeed, such containers need to have very goodmechanical strength to withstand, for example, the rigours of transport,storage and use. These rigours include e.g. stacking of bottles on topof each other (topload), vibrations, shaking and other mechanicalstresses, additionally temperature fluctuations during transportation,and usual handling stresses, such as being dropped and squeezed duringconsumer use. Thus, important mechanical properties include resistanceto compression and flexion, and temperature fluctuations. However, thesecontainers must have, at the same time, a weight as low as possible inorder to keep material consumption and the resulting environmentalfootprint, as well as transportation effort, low. In addition, suchcontainers are also required to provide a high level of aesthetic appealto consumers.

Polypropylene is a polyolefin (or polyalkene) compound and is derivedfrom crude oil. Environmental, economic and sustainability questions arerestricting the use of products derived from this limited resource.Therefore, there is a desire to identify more sustainable and effectivematerials that can be used to replace or partially replace thepolyolefin component, whilst meeting the physical requirements discussedabove.

The use of fillers to replace some of the thermoplastic material, oreven to change the properties of thermoplastic materials, is known inthe art. For example, carbon black is known to accelerate thedegradation of polypropylene following exposure to UV light.Furthermore, various inorganic fillers have been used in combinationwith polyethylene—kaolin, mica, diatomite and talc, for example. Thesefillers tend to be economically affordable and widely available.

Injection moulding, described hereinafter, is a very commonly usedprocess for manufacturing such containers. In conventional injectionmoulding processes the rate-limiting step of the moulding cycle is thecooling step, which correlates with the thickness of the moulded part.Energy is stored as heat across the gauge of the part and must betransferred into the mould during the cooling cycle. Hence parts with alower surface area to volume ratio cool more slowly. Cooling time has asignificant impact on the speed and hence production capacity ofinjection moulding equipment, ultimately translating into a greaternumber of production stations.

There is a need, therefore, for the provision of an improved process formaking injection-moulded parts, which maintains the suitable physicalproperties of the resultant moulded parts, such as mechanical strengthand resistance to temperature. In addition, the moulded part must have alow weight and good aesthetic properties. Also, there is a need for thematerials from which the part is made to be economically andecologically sound and to demonstrate sustainability.

SUMMARY OF THE INVENTION

In a first embodiment, the present invention relates to an injectionmoulded polymeric household bottle cap made of a polypropylenecomposition comprising:

-   -   from 3% to 17% particulate CaCO₃ by total weight of the        composition;    -   from 0% to 6% additive by total weight of the composition; and,    -   qsp polypropylene;        wherein the polypropylene composition in its solid form and with        average wall thickness T has a flexural modulus, measured        according to ASTM D790-07, being at least 95% of the flexural        modulus measured on a reference polypropylene composition        substantially free of CaCO₃ and having average wall thickness of        at least T+10%.

In a second embodiment the invention relates to packaging for ahousehold product comprising: a container suitable for containing ahousehold composition; an injection moulded polymeric household bottlecap as defined in the first embodiment, mounted onto said container andbeing suitable for sealing said container and for dispensing saidhousehold composition.

In a third embodiment, the invention relates to a household productcomprising: a container; a household composition, contained in saidcontainer; an injection moulded polymeric household bottle cap asdefined in the first embodiment, mounted onto said container.

In a fourth embodiment, the invention relates to the use of a bottlecap, as defined in the first embodiment, for providing a moresustainable and/or environmentally friendly household packaging comparedto a reference polypropylene bottle cap being substantially free ofCaCO₃.

In a fifth embodiment, the invention relates to a method of producing aninjection moulded bottle cap, as defined in the first embodiment,comprising the steps of:

(a) providing a polypropylene composition in a molten form;

(b) injecting said polypropylene composition into a mould to form saidbottle cap;

(c) cooling said polypropylene composition to solidify it;

(d) ejecting said bottle cap from the mould;

(e) preparing the mould for moulding the next bottle cap.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of a bottle cap is depicted in FIGS. 1 to 4 in an openconfiguration:

FIG. 1 shows a perspective view.

FIG. 2 shows the cap from above.

FIG. 3 shows a front elevation of the cap.

FIG. 4 depicts a cross-section across line X shown on FIG. 2.

FIG. 5 shows flexural modulus (λ) and stress (σ) values forpolypropylene compositions comprising varying amounts of Omyalene® 102 M(CaCO₃).

DETAILED DESCRIPTION OF THE INVENTION

The inventors have surprisingly found that utilising a specificproportion of CaCO₃ particles in combination with polypropylene (alsoreferred to as PP herein) results in a material with markedly improvedmechanical properties. In particular, said material exhibits an improvedflexural modulus. In the context of a bottle cap, the inventors havesurprisingly found that said improved mechanical properties allow theaverage wall thickness of the bottle cap to be down-gauged. This enablesdesirable cap weight reduction, whilst maintaining said mechanicalproperties above the thresholds necessary for the cap to endure, withminimal damage, the required rigours, e.g. transportation and use. CaCO₃has a whitening effect on parts and thus a lower amount of whiteningagent e.g. TiO₂ is required. Also, PP comprising CaCO₃ wears injectionmoulding machinery more slowly than PP comprising TiO₂. Additionally,said material meets economic and sustainability questions. Furthermore,said material exhibits a density such that it floats in water, whichallows normal bottle sorting to occur i.e. it does not requiredifferent, and hence undesirable, recycling methods, compared toconventional polypropylene. Moreover, the lower heat capacity andincreased thermal conductivity of said material results in a reducedmould cycle time—the cooling process step can be shortened compared tothe same injection moulding process using conventional polypropylene asa control/reference following injection into the mould.

As used herein, the terms: “substantially free of CaCO₃” means comprisesless than 1%, preferably less than 0.5%, more preferably less than 0.1%,even more preferably 0%; “part” means a component portion of a finalproduct.

All percentages are by weight unless otherwise stated.

In the first embodiment, the present invention relates to an injectionmoulded polymeric household bottle cap made of a PP compositioncomprising:

-   -   from 3% to 17% particulate CaCO₃ by total weight of the        composition;    -   from 0% to 6% additive by total weight of the composition; and,    -   qsp PP;        wherein the PP composition in its solid form and with average        wall thickness T has a flexural modulus, measured according to        ASTM D790-07, being at least 95% of the flexural modulus        measured on a reference PP composition substantially free of        CaCO₃ and having average wall thickness of at least T+10%.

The present invention relates to an injection moulded polymerichousehold bottle cap made of a PP composition. PP is a thermoplasticpolymer made from 1-propene monomers, which are derived from crude oil,and has a melting point of ˜160° C. Suitable commercially available PPsinclude: grade PP 575-5 from SABIC-KSA (Saudi Basic IndustriesCorporation, Kingdom of Saudi Arabia), Riyadh, Saudi Arabia; thehomo-polymer European Moplen HP501L and the Moplen PP Random CopolymerRP340N, both from LyondellBasell Polymers, Houston, USA.

Said PP composition comprises particulate CaCO₃ (calcium carbonate).CaCO₃ is found naturally in various rocks and minerals, such asaragonite, calcite, vaterite, chalk, limestone, marble and travertine.The PP composition comprises from 5% to 14% CaCO₃, more preferably thePP composition comprises from 8% to 11% CaCO₃, by weight of the finalcomposition. Said particulate CaCO₃ has a particle size of 2 to 4 μm.Particle size is commonly represented by the term d₅₀. A d₅₀ of 2 μmmeans 50% of the particles have a diameter of less than 2 μm. Using aparticle size of above 4 μm is undesirable because larger particle sizesmay result in the initiation of cracks in PP parts. A suitablecommercially available CaCO₃ source as a filler for the presentinvention includes the granulated CaCO₃ product Omyalene® 102 M fromOmya AG, Oftringen, Switzerland, which comprises 84% CaCO₃, 15% PP and˜1% stearic acid.

Said PP composition also comprises at least one additive. Said PPcomposition comprises from 0% to 6% additive, more preferably from 0% to3% additive, by weight of the final composition. Additives may beselected from the group consisting of impact modifiers; dispersants;fillers; filler coatings; foaming agents; processing agents; lubricants;particles; dyes and colorants; UV filters; anti-static agents; andmixtures thereof. When particles are used as additives, said particlesare different from particulate CaCO₃ as defined above. Additives used inthe PP composition according to the present invention are conventionaladditives i.e. present in a conventional PP carrier mix. Particles maybe used e.g. Expancel® microspheres from Akzo Nobel, Essen, Germany,and/or foaming agents e.g. Hydrocerol® from Clariant, Frankfurt-Höchst,Germany. Furthermore, different fillers may be utilised in addition toCaCO₃, for example kaolin, carbon black, mica, silica, diatomite,nano-particle clays, cellulose fibre, wood fibre, powdrous wood or chinagrass, rice spelt, starch and talc. With the addition of such additivesthe process may achieve further benefits such as increased displacementof PP resin, increased cycle time reduction, no yellowing side effects,and better part integrity.

The PP composition in its solid form and with average wall thickness Thas a flexural modulus, measured according to ASTM D790-07, of at least95% of the flexural modulus measured on a reference PP compositionsubstantially free of CaCO₃ and having average wall thickness of atleast T+10%. ATSM stands for American Society for Testing and Materials,which is now known as ATSM International. The flexural modulus can bemeasured using ASTM D790-07, which is a standard test method forflexural properties of unreinforced and reinforced plastics andelectrical insulating materials by three-point bending.

Average wall thicknesses of bottle caps can be measured with a calliperdevice. FIG. 4 shows the average wall thickness of a bottle cap, whereinthe wall of the cap is shown as a cross-hatched portion (F), which hasan average wall thickness (T). In an embodiment, the bottle cap has anaverage wall thickness T of at least 10% lower than the average wallthickness of a reference polypropylene bottle cap substantially free ofCaCO₃. More preferably the average wall thickness T is reduced by atleast 20%. In an embodiment, the bottle cap has a average wall thicknessT of preferably from 0.5 mm to 10 mm, more preferably 0.5 mm to 1.5 mm

In an embodiment, the polypropylene composition in its solid form has acompression stability, measured according to ASTM D2659, of at least 10%higher than compression stability of a reference PP compositionsubstantially free of CaCO₃. The compression stability can be measuredusing ASTM D2659, which is a standard test method for column crushproperties of blown thermoplastic containers.

According to the present invention the PP composition preferablyexhibits a reduced specific heat capacity compared to a reference PPcomposition substantially free of CaCO₃. The specific heat capacity of amaterial can be measured by modulated temperature differential scanningcalorimetry, e.g. ASTM WK 12876.

Also preferably, the PP composition exhibits an increased thermalconductivity compared to reference PP composition substantially free ofCaCO₃. Thermal conductivity can be measured by e.g. ASTM StandardD5930-01, a standard test method for thermal conductivity of plastics bymeans of a transient line-source technique.

Typical density, thermal conductivity and heat capacity values for PPand calcite (CaCO₃) are shown in Table I below.

TABLE I Polypropylene Calcite Density (g · cm⁻³) 0.92 2.7 Heatconductivity  0.1-0.22 1.5-4   (W · m⁻¹ · K⁻¹) Heat capacity (J · K⁻¹ ·kg⁻¹) 1700-1900 700-900

PP items are commonly desired to be recycled. A typical method ofrecycling such items involves shredding and subsequent floatationsorting via density relative to water. PP floats in water whereas someother plastics sink. Preferably, the PP composition according to thepresent invention still exhibits a density such that it floats in water,which allows normal bottle sorting to occur i.e. it does not requiredifferent, and hence undesirable, recycling methods, compared to PPwithout CaCO₃.

The present invention relates to an injection moulded polymerichousehold bottle cap. Conventional bottle caps comprise a main bodyportion, an orifice and a closure, but vary in sizes and dimensions.FIGS. 1 to 4 show a typical flip top bottle cap, which is known fromProcter & Gamble Company products e.g. Pantene®. As shown in FIGS. 1 to4, the flip top bottle cap, made from a PP composition according to thepresent invention, comprises a receiving portion (A); a hinged sealingportion (B); a sealing portion (C); a dispensing portion (D); and ahinge (E).

According to the present invention, the bottle cap meets performancetest requirements such that it is able to withstand the rigours oftransportation and use, e.g. cap opening force, pull off force, leakresistance, hinge flex, impact resistance, stress crack resistance, faderesistance, and resistance to the product contained within the bottle.

In an embodiment, the PP composition is stable over a period of time ofat least 6 months, preferably from 12 to 24 months, when exposed to atemperature from 25 to 45° C., a relative humidity from 20% to 60%, andexposure to light of 2700 Kelvin to 3300 Kelvin. Exposure to light ismeasured by the correlated colour temperature.

More preferably the bottle cap or closure is suitable for sealing acontainer comprising a household composition and for dispensing saidhousehold composition. Household compositions may be selected from thegroup consisting of: personal care compositions, cleansing compositions,fabric care compositions, and homecare compositions. Said householdcomposition is preferably a personal care composition, more preferably ahair care composition. Hair care compositions may comprise any suitablehair care agents, preferably hair care agents selected from the groupconsisting of hair conditioning agents, hair styling agents, perming andwaving agents, hair cleansing agents, hair colouring, dyeing agents,bleaching agents, hair shine or gloss imparting agents, and mixturesthereof.

In a second embodiment the invention relates to packaging for ahousehold product comprising: a container suitable for containing ahousehold composition; an injection moulded polymeric household bottlecap as defined in the first embodiment, mounted onto said container andbeing suitable for sealing said container and for dispensing saidhousehold composition. Typical household compositions are defined above.

In a third embodiment, the invention relates to a household productcomprising a container; a household composition, contained in saidcontainer; an injection moulded polymeric household bottle cap asdefined in the first embodiment, mounted onto said container. Typicalhousehold compositions are defined above.

In a fourth embodiment, the invention relates to the use of a bottlecap, as defined above, for providing a more sustainable and/orenvironmentally friendly household packaging compared to a reference PPbottle cap being substantially free of CaCO₃.

In a further embodiment, the household product forms part of a kit. Thekit may comprise the packaging as described above; a label for thecontainer; further packaging items; and/or a plurality of householdproducts. The kit may be assembled within a package, e.g. shrinkwrapping, a box. The kit may comprise instructions comprisinginformation and directions on to prepare, use, and/or apply thehousehold product composition. The instructions may further include oneor more illustrations.

In a fifth embodiment, the invention relates to a method of producing aninjection moulded bottle cap, as defined in the first embodiment,comprising the steps of: providing a polypropylene composition in amolten form; injecting said polypropylene composition into a mould toform said bottle cap; cooling said polypropylene composition to solidifyit; ejecting said bottle cap from the mould; preparing the mould formoulding the next bottle cap.

Injection moulding is a commonly used process for the manufacture ofhousehold items. Often blow moulding is used for containers andinjection moulding is used for smaller and more complex parts such asbottle caps. Conventional injection moulding processes comprise thesteps: injecting molten thermoplastic material (such as PP) into a mouldto form the derived part; cooling said thermoplastic material (PP) longenough for it to solidify; opening the mould to allow access andejection of the solidified part; closing the mould for the next cycle.More specifically, the process firstly involves injecting a moltenthermoplastic composition into a cavity formed in a so-called mould,which consists of at least two pieces capable of being opened to releasethe solidified piece formed as a negative version of the cavity. A mouldis also sometimes referred to as a die. After injection, the plastic isallowed to cool (usually actively cooled) and hence solidify. Thentypically the mould is opened and the moulded part is ejected or removedfrom the mould. The mould then closes in preparation for the next cycle.

According to an embodiment of the present invention the time of thecooling step is shortened by at least 1.5% compared to said processusing a reference PP composition substantially free of CaCO₃. For thepurposes of this application, the cooling time starts when the injectionstep is complete and ends when the bottle cap has been ejected i.e. whenthe injection step (b) is complete and ends when the part has beenejected (step [d]). Preferably the cooling step is shortened by at least10%, more preferably by at least 25%. Furthermore, the cooling step isshortened by at least 1 s, more preferably by at least 2 s, even morepreferably by at least 3 s.

Examples

The following examples further describe and demonstrate the preferredembodiments within the scope of the present invention. The examples aregiven solely for the purpose of illustration, and are not to beconstrued as limitations of the present invention since many variationsthereof are possible without departing from its scope.

FIG. 5 shows the mechanical data resulting following measurement of theflexural modulus via test method ASTM D790-07 for PP compositionscomprising varying percentages of Omyalene® 102 M (84% CaCO₃) i.e. 0%,5%, 10% and 15%. Two different PP resins were compared, Moplen HP501Land Moplen RP340N. The lighter coloured bars show the flexural modulus(λ) data and the darker coloured bars the stress (σ) data, which wascalculated as described below.

To calculate flexural strain (ε_(f)) for a sample:

ε_(f)=(6·D·d)/L ²  (I)

Where D is displacement, d is thickness, and L is length of span. ForFIG. 5, D is 5 mm and L is 25.4 mm. For all bars, the thickness of thesample was 1 mm, except the second set of bars, which used a 2 mm thicksample, as indicated. The stress (σ) and flexural strain (ε_(f)) arelinked to flexural modulus (λ) in the following relationship:

Flexural Modulus=Stress/Flexural Strain  (II)

λ=σ/ε_(f)

Therefore:

Stress=Flexural Modulus×Flexural Strain  (III)

σ=λ·ε_(f)

Substituting flexural strain from formula I into formula III, the stressa sample can withstand can be calculated. FIG. 5 shows the stressincreases with increasing percentage of CaCO₃ in the PP composition dueto increased flexural modulus.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. An injection moulded polymeric household bottlecap made of a polypropylene composition comprising: from about 3% toabout 17% particulate CaCO₃ by total weight of the composition; fromabout 0% to about 6% additive by total weight of the composition; and,qsp polypropylene; wherein the polypropylene composition in its solidform and with average wall thickness T has a flexural modulus being atleast about 95% of the flexural modulus measured on a referencepolypropylene composition substantially free of CaCO₃ and having averagewall thickness of at least about T+10%.
 2. A bottle cap, according toclaim 1, wherein the polypropylene composition in its solid form has acompression stability of at least about 10% higher than compressionstability of a reference polypropylene composition substantially free ofCaCO₃.
 3. The bottle cap, according to claim 1, wherein thepolypropylene composition is stable over a period of time of at least 6months, preferably from about 12 to about 24 months, when exposed to atemperature from about 25 to about 45° C., a relative humidity fromabout 20% to about 60%, and exposure to light of about 2700 Kelvin toabout 3300 Kelvin.
 4. The bottle cap, according to claim 1, wherein thepolypropylene composition comprises from about 5% to about 14%particulate CaCO₃, by weight of the total composition.
 5. The bottlecap, according to claim 1, wherein the polypropylene compositioncomprises from about 8% to about 11% particulate CaCO₃, by weight of thetotal composition.
 6. The bottle cap, according to claim 1, wherein saidpolypropylene composition comprises from about 0% to about 3% additive,by weight of the final composition.
 7. The bottle cap, according toclaim 1, wherein additive is selected from the group consisting of:impact modifiers; dispersants; fillers; filler coatings; foaming agents;processing agents; lubricants; particles; dyes and colorants; UVfilters; anti-static agents; and mixtures thereof.
 8. The bottle cap,according to claim 1, wherein said cap is suitable for sealing acontainer comprising a household composition and for dispensing saidhousehold composition.
 9. The bottle cap, according to claim 1,comprising a dispensing orifice, a receiving portion, and hinged sealingportion.
 10. The bottle cap, according to claim 1, wherein the bottlecap has an average wall thickness T of at least about 10% lower than theaverage wall thickness of a reference polypropylene bottle capsubstantially free of CaCO₃.
 11. The bottle cap, according to claim 1,wherein the bottle cap has an average wall thickness T is reduced by atleast about 20% than the average wall thickness of a referencepolypropylene bottle cap substantially free of CaCO₃.
 12. The bottlecap, according to claim 1, having an average wall thickness from about0.5 mm to about 10 mm.
 13. The bottle cap, according to claim 1, havingan average wall thickness from about 0.5 mm to about 1.5 mm.
 14. Thebottle cap, according to claim 1, said particulate CaCO₃ has a particlesize of about 2 to about 4 μm.
 15. The bottle cap, according to claim 1,wherein the polypropylene composition comprises microspheres and/orfoaming agents.
 16. Packaging for a household product comprising: acontainer suitable for containing a household composition; an injectionmoulded polymeric household bottle cap according to claim 1, mountedonto said container and being suitable for sealing said container andfor dispensing said household composition.
 17. A household productcomprising: a container; a household composition, contained in saidcontainer; an injection moulded polymeric household bottle cap accordingto claim 1, mounted onto said container.
 18. The household product,according to claim 17, wherein said household composition is selectedfrom the group consisting of personal care compositions, cleansingcompositions, fabric care compositions, homecare compositions, andcombinations thereof.
 19. A household product, according to claim 18,wherein said household composition is a hair care composition comprisinga component selected from the group of hair conditioning agents, hairstyling agents, perming and waving agents, hair cleansing agents, haircolouring, dying or bleaching agents, hair shine or gloss impartingagents, and mixtures thereof.
 20. A method of producing an injectionmoulded bottle cap, according to claim 1, comprising the steps of: (a)providing a polypropylene composition in a molten form; (b) injectingsaid polypropylene composition into a mould to form said bottle cap; (c)cooling said polypropylene composition to solidify it; (d) ejecting saidbottle cap from the mould; (e) preparing the mould for moulding the nextbottle cap.